Mobile telephones and other portable electronic devices increasingly include a locating feature that enables a current geographic location of a device to be either displayed on the device or transmitted to a remote receiver. These features are generally called location services (abbreviated as LCS, for “LoCation Services”). LCS features that display location coordinates on a device are useful, for example, to device users who need to know where they are located relative to geographic map coordinates. Thus LCS features can enable a device user to initiate a location request where the device acts as a Global Positioning System (GPS) terminal. Also, location requests may be initiated by third parties and transmitted to a device over a wireless network. Such third party requests are useful in various circumstances. For example, mobile telephone networks may be able to improve network efficiency and provide better Quality of Service (QoS) and roaming rates to a mobile user if the network can periodically monitor a mobile telephone location. Also, emergency services can sometimes save lives by rapidly and accurately identifying where emergency phone calls have originated. Other useful location-based services and data that can be provided through portable electronic devices include maps, weather forecasts, traffic data, and local news.
Various locating technologies can be used to determine the location of a portable electronic device. For example, the Global Positioning System (GPS) can be used to identify a location anywhere in the world of some mobile telephones. However, because most mobile telephones are already operatively connected to land-based network stations, and do not need to communicate solely with satellites, Assisted GPS (A-GPS) services are commonly used to incorporate better and more efficient location services into mobile telephones. Secure User Plane Location (SUPL) is a technology developed by the Open Mobile Alliance (OMA) that concerns the transfer of assistance data and positioning data between a portable electronic device and a location platform, and includes a family of standards. A “user plane” means that assistance data and positioning data are transmitted between the device and the location platform over a conventional wireless communication channel such as a General Packet Radio Service (GPRS) channel. User plane communications are thus distinguished from control plane communications where assistance data and positioning data are transmitted between a device and a location platform over a separate signaling channel in a network.
Other locating technologies include short-range wireless based locating technologies, also known as real time location services (RTLS), which measure parameters of a wireless local area network (WLAN), such as a received signal strength indicator (RSSI) or a time difference of arrival (TDOA) parameter. Still other locating technologies include other hybrid approaches that employ a combination of satellite based, cell based, and short-range wireless based locating technologies.
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